N109T

HISTORY OF FLIGHTOn September 12, 2023, about 2047 Alaska daylight time (AKDT), a Piper PA-18-150, N109T, sustained substantial damage when it was involved in an accident near St. Mary’s, Alaska. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 135 on-demand flight.

Two days before the accident, the pilot ferried a group of five hunters, a guide, and their equipment from the operator’s base in Holy Cross, Alaska, to an airstrip in St Mary’s. The group then set up camp next to the runway, which was oriented north-south within hilly terrain about 70 miles northwest of Holy Cross.

The group planned to hunt for a moose and prepare it for transportation back to the operator’s base. The day before the accident, the group successfully hunted a moose and coordinated with the pilot via satellite messaging devices to ferry the meat the next day. On the day of the accident, the pilot arrived at the camp about 1540. The pilot and hunters loaded the airplane with the first batch of meat, and the airplane departed on the north runway. After takeoff, the airplane made an uneventful climbing right turn over an adjacent ridgeline that paralleled the airstrip to the east and then continued in the general direction of Holy Cross.

The pilot returned to camp about 1940 for the second and final load. The meat was strapped into the rear passenger seat area by the pilot with both the seatbelt and rope and was also loaded into the airplane’s belly pod, which did not have tie-down provisions. The pilot then tied the moose antlers to the right wing strut; the antlers were cupped outward and perpendicular to the direction of flight.

They discussed the weather and observed that the wind at the airstrip was generally calm and from the north, but was also intermittently variable and gusting. Members of the group reported to the pilot that the wind was gusting much stronger at the northern (departure) end of the airstrip.

The pilot then boarded the airplane and positioned it for a takeoff to the north. The hunters noticed that the ground roll was slightly longer than before, and that the airplane appeared to be more heavily loaded and “labored” than during the previous flight. They stated that, as the airplane reached the end of the airstrip, it pitched up and turned sharply to the right; however, rather than climbing as before, it flew behind the adjacent ridgeline and out of view. The group initially thought that the pickup had been successful, and they cheered with relief, but the airplane did not reappear from behind the ridge. They ran to the top of the ridgeline, looked down, and saw that the airplane had crashed.

One of the hunters recorded a video of the takeoff. The video showed that the airplane began the ground roll at the southern end of the airstrip and departed uphill to the north. The flaps were retracted, and the tail of the airplane came up as soon as the pilot applied engine power (see figure 1). The ground roll lasted about 530 ft, and immediately after takeoff, the airplane pitched up and rolled right (see figure 2). The airplane then rolled to a wings-level attitude, and the video ended a few seconds later. The engine was heard operating during the recording and the airplane was not trailing smoke or vapor.

Figure 1. Airplane during the takeoff roll (Source: hunter video).

Figure 2 - Airplane rolling right immediately after takeoff (Source: hunter video). PERSONNEL INFORMATIONThe pilot was first issued his pilot certificate in 1993. His logbook was not recovered; however, at the time of his last FAA medical examination on August 11, 2023, he reported a total flight experience of 6,707 hours.

The pilot was the operator’s sole pilot. He was added to the company’s operating specifications and underwent a checkride with an FAA inspector, in accordance with 14 CFR 135.293 and 135.299, ten days before the accident. The series of flights that preceded the accident were the first in his capacity as a pilot for the operator. He had been a friend of the operator for many years, and according to the operator he had flown the airplane many times before. AIRCRAFT INFORMATIONThe airplane was originally manufactured in 1952 as a Piper PA-18-105 (“Special”), under the Type Certificate number 1A2. At that time, it was equipped with a Lycoming O-235-C1 engine. A series of major alterations were performed through STC in 2013. These included a replacement fuselage and new horizontal and vertical stabilizers, rudder, and elevators. Additional major alterations and repairs included the replacement of the original engine with a Lycoming O-320, 160-hp engine; a belly-mounted cargo pod; new seats; replacement of both forward wing spars and one rear wing spar; replacement of a series of wing ribs; extended flaps; installation of vortex generators; and 35-inch Alaska Bushweel main wheels and tires (which included an upgraded landing gear strut/suspension assembly).

The FAA released Advisory Circular (AC) 20-188 on December 9, 2016. The AC

provided engineering guidance to installers for determining the compatibility of the installation of approved changes via STC where previously approved changes were installed on aircraft.

The airplane was involved in an accident in 2017, which required replacement of the vertical stabilizer and rudder, along a series of wing ribs, the aft spar of the right wing, and the forward spar of the left wing.

As a result of the major repairs and alterations performed at the time of the accident, almost none of the original airplane remained. METEOROLOGICAL INFORMATIONThe National Weather Service (NWS) Surface Analysis Chart centered over Alaska for 2200 AKDT depicted a low-pressure system at 1000-hectopascals (hPa) located along the Alaskan Peninsula with two low-pressure systems at 1001-hPa located in the northern Bering Strait with a trough stretched from the 1000-hPa to the 1001-hPa low pressure systems. The accident site was located west of the surface trough.

The station model closest to the accident site depicted an air temperature of 42°F, a dew point temperature of 40°F, cloudy skies, and a northwest wind at 10 knots (kts). These findings were corroborated by the witnesses at the accident site and the video recording of the takeoff.

Before takeoff, the pilot discussed the weather with the hunting group, and they noted that while winds on the runway were generally out of the north, there were intermittent gusts from random directions. They discussed how, during the previous flight that day, the winds in the valley below were gusting and generally out of the east and southeast, but were calm on the runway.

Archived Weather data retrieved from the NWS Aviation Weather Center (AWC) experimental website for 2045 included low-level wind data from the surface. This data indicated a 10- to 15-knot north wind over the accident site at 2045.

The NWS Winds and Temperature Aloft forecast issued at 1759 and valid for the closest points to the accident indicated wind at 3,000 ft msl out of the north at 12-13 kts.

A search of archived information indicated that the pilot did not request weather information from Alaskan Flight Services. A search of ForeFlight information indicated that he did not have a ForeFlight account. It is unknown what weather information, if any, the pilot checked or received before or during the accident flight. AIRPORT INFORMATIONThe airplane was originally manufactured in 1952 as a Piper PA-18-105 (“Special”), under the Type Certificate number 1A2. At that time, it was equipped with a Lycoming O-235-C1 engine. A series of major alterations were performed through STC in 2013. These included a replacement fuselage and new horizontal and vertical stabilizers, rudder, and elevators. Additional major alterations and repairs included the replacement of the original engine with a Lycoming O-320, 160-hp engine; a belly-mounted cargo pod; new seats; replacement of both forward wing spars and one rear wing spar; replacement of a series of wing ribs; extended flaps; installation of vortex generators; and 35-inch Alaska Bushweel main wheels and tires (which included an upgraded landing gear strut/suspension assembly).

The FAA released Advisory Circular (AC) 20-188 on December 9, 2016. The AC

provided engineering guidance to installers for determining the compatibility of the installation of approved changes via STC where previously approved changes were installed on aircraft.

The airplane was involved in an accident in 2017, which required replacement of the vertical stabilizer and rudder, along a series of wing ribs, the aft spar of the right wing, and the forward spar of the left wing.

As a result of the major repairs and alterations performed at the time of the accident, almost none of the original airplane remained. WRECKAGE AND IMPACT INFORMATIONThe runway was situated at the crest of a hill, where terrain rapidly fell away into a valley at the northern departure end. The terrain then began to climb, such that within about ¾ mile, it was 400 ft higher than the runway.

The airplane came to rest on a 30° downward slope on the other side of the adjoining ridgeline, at an elevation of 1,210 ft mean sea level, about 10 ft lower and 600 ft east of the departure end of the airstrip (see figure 3). The surrounding area consisted of rolling hills covered in tundra, grass, and low-lying shrubs and bushes.

Figure 3 - Accident site.

The fuselage came to rest on a northerly heading, and both wings remained partially attached and generally in line with each other on a northwest-southeast orientation. The first identified point of impact was located about 20 ft below the main wreckage, and consisted of a divot in the soil that contained blue and white fragments that matched the right wingtip (see figure 4). The right wing landing light assembly and right window frame were located about 5 ft uphill in a westerly direction. A large divot i...